Gesture recognition system and method of using same

ABSTRACT

A method of executing a gesture command includes identifying a hand centroid of a hand. The method also includes identifying a first finger tip of a first finger on the hand. The method further includes identifying a thumb tip of a thumb on the hand. Moreover, the method includes determining a surface normal relationship between the hand centroid, the first fingertip and the thumb tip.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present disclosure is a continuation of U.S. patent application Ser.No. 16/980,263, filed Sep. 11, 2020, entitled “Gesture RecognitionSystem and Method of Using Same,” which claims priority to PCTApplication No. PCT/US2019/021872, filed on Mar. 12, 2019, entitled“Gesture Recognition System and Method of Using Same,” which claimspriority to U.S. Provisional Patent Application No. 62/642,533, filed onMar. 13, 2018, entitled “Gesture Recognition System and Method of UsingSame.” The contents of the aforementioned patent applications are herebyexpressly and fully incorporated by reference in their entirety, asthough set forth in full.

FIELD OF THE INVENTION

The present disclosure relates to mixed reality systems includinggesture recognition systems, and methods for using same.

BACKGROUND

Modern computing and display technologies have facilitated thedevelopment of “mixed reality” or “MR” systems for so called “virtualreality” or “augmented reality” experiences, wherein digitallyreproduced images or portions thereof are presented to a user in amanner wherein they seem to be, or may be perceived as, real. A virtualreality, or “VR”, scenario typically involves presentation of digital orvirtual image information without transparency to actual real-worldvisual input. An augmented reality, or “AR”, scenario typically involvespresentation of digital or virtual image information as an augmentationto visualization of the actual world around the user (i.e., transparencyto other actual real-world visual input). Accordingly, AR scenariosinvolve presentation of digital or virtual image information withtransparency to other actual real-world visual input.

Various optical systems generate images at various depths for displayingmixed reality (VR and AR) scenarios. Some such optical systems aredescribed in U.S. U.S. Utility patent application Ser. No. 14/555,585filed on Nov. 27, 2014 (attorney incorporated by reference in theirentirety, as though set forth in full.

Mixed reality systems typically employ wearable display devices (e.g.,head-worn displays, helmet-mounted displays, or smart glasses) that areat least loosely coupled to a user's head, and thus move when the user'shead moves. If the user's head motions are detected by the displaysystem, the data being displayed can be updated to take the change inhead pose (i.e., the orientation and/or location of user's head) intoaccount.

As an example, if a user wearing a head-worn display views a virtualrepresentation of a three-dimensional (3-D) object on the display andwalks around the area where the 3-D object appears, that 3-D object canbe re-rendered for each viewpoint, giving the user the perception thathe or she is walking around an object that occupies real space. If thehead-worn display is used to present multiple objects within a virtualspace (for instance, a rich virtual world), measurements of head posecan be used to re-render the scene to match the user's dynamicallychanging head location and orientation and provide an increased sense ofimmersion in the virtual space. However, there is an inevitable lagbetween rendering a scene and displaying/projecting the rendered scene.

Head-worn displays that enable AR provide concurrent viewing of bothreal and virtual objects. With an “optical see-through” display, theuser can see through transparent (or semi-transparent) elements in thedisplay system to view directly the light from real objects in theenvironment. The transparent element, often referred to as a “combiner,”superimposes light from the display over the user's view of the realworld, where light produced by the display projects an image of thevirtual content over the see-through view of the real world. A camera(e.g., a field of view or FOV camera) may be mounted onto the wearabledisplay to capture images or videos of the scene being viewed by theuser.

Current 3-D optical systems, such as those in mixed reality systems,optically render virtual objects. Objects are “virtual” in that they arenot real physical objects located in respective positions in 3-D space.Instead, virtual objects only exist in the brains (e.g., the opticalcenters) of viewers and/or listeners when stimulated by light beamsdirected to the eyes of audience members.

MR systems allow virtual objects to interact with real world physicalobjects. Some of these interactions make use of user input. Mixedreality systems can receive user input through gesture recognitionsub-systems, thereby eliminating separate input devices (e.g.,keyboards, mice, joysticks, totems, etc.) from the mixed realitysystems. Examples of such gesture recognition system are described inU.S. U.S. Utility patent application Ser. No. 14/331,218 filed on Jul.14, 2014 (attorney docket number ML-30020.00), the contents of which arehereby expressly and fully incorporated by reference in their entirety,as though set forth in full. In such systems, a user's hands function asthe input devices. However, the complexity of the human hand and it'swide range of articulation complicates gesture recognition. There existsa need for more accurate and precise/repeatable gesture recognition andsystems for accomplishing same.

SUMMARY

In one embodiment, a method of executing a gesture command includesidentifying a hand centroid of a hand. The method also includesidentifying a first finger tip of a first finger on the hand. The methodfurther includes identifying a thumb tip of a thumb on the hand.Moreover, the method includes determining a surface normal relationshipbetween the hand centroid, the first fingertip, and the thumb tip.

In one or more embodiments, the surface normal relationship includesrespective surface normals at the hand centroid on a caudal surface ofthe hand, at the first fingertip, and at the thumb tip are substantiallyparallel. A virtual cursor may be displayed in a field of view at alocation corresponding to the first fingertip. The method may alsoinclude detecting a movement of the thumb tip to a mapped planarposition between the hand centroid and the first fingertip, andexecuting a command at the cursor location in response to detecting themovement.

In one or more embodiments, the surface normal relationship includes asurface normal at the hand centroid on a caudal surface of the hand issubstantially orthogonal to the respective surface normals at the firstfingertip and at the thumb tip. A virtual cursor may be displayed in afield of view at a location between the first fingertip and the thumbtip. The method of may also include detecting that a first fingertipposition of the first fingertip and a thumb tip position of the thumbtip are substantially similar, and executing a command at the cursorlocation in response to detecting of the substantially similar firstfingertip and thumb tip positions.

In one or more embodiments, the hand centroid, the first fingertip, andthe thumb tip are outside of a field of view of a user. In otherembodiments, the hand centroid, the first fingertip, and the thumb tipmay be inside of a field of view of a camera worn by the user.

In another embodiment, a method of executing a gesture command includesidentifying a hand centroid of a hand. The method also includesidentifying a first finger tip of a first finger on the hand. The methodfurther includes identifying a thumb tip of a thumb on the hand.Moreover, the method includes calculating a first line between the firstfingertip and the hand centroid. In addition, the method includescalculating a second line between the thumb tip and the hand centroid.The method also includes determining an angular relationship between thefirst and second lines.

In one or more embodiments, the angular relationship is that the firstand second lines are substantially orthogonal. A virtual cursor maydisplayed in a field of view at a location corresponding to the firstfingertip. The method may also include detecting a change in the angularrelationship between the first and second lines, and executing a commandat the cursor location in response to detecting the change in theangular relationship. The change in the angular relationship may be athreshold amount of decrease in an angle between first and second lines.The threshold amount of decrease may be about 30 degrees.

Additional and other objects, features, and advantages of the inventionare described in the detail description, figures and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate the design and utility of various embodiments ofthe present invention. It should be noted that the figures are not drawnto scale and that elements of similar structures or functions arerepresented by like reference numerals throughout the figures. In orderto better appreciate how to obtain the above-recited and otheradvantages and objects of various embodiments of the invention, a moredetailed description of the present inventions briefly described abovewill be rendered by reference to specific embodiments thereof, which areillustrated in the accompanying drawings. Understanding that thesedrawings depict only typical embodiments of the invention and are nottherefore to be considered limiting of its scope, the invention will bedescribed and explained with additional specificity and detail throughthe use of the accompanying drawings in which:

FIG. 1 depicts a user's view of augmented reality (AR) through awearable AR user device according to one embodiment.

FIG. 2 depicts an AR system including a gesture recognition systemaccording to one embodiment.

FIGS. 3-11 are schematic diagrams illustrating gesture recognitionaccording to various embodiments.

FIG. 12 is a process flow diagram of an exemplary method of performingan action based on a recognized gesture according to one embodiment.

FIG. 13 is a plan view illustrating various finger gestures according tovarious embodiments.

FIGS. 14-20 are a series of plan views illustrating steps in a method ofrecognizing a gesture and performing an action based on the recognizedgesture according to one embodiment.

FIGS. 21-26 are a series of plan views illustrating steps in a method ofrecognizing a gesture and performing an action based on the recognizedgesture according to another embodiment.

FIG. 27 is a block diagram schematically depicting an illustrativecomputing system suitable for implementing an embodiment of the presentdisclosure.

DETAILED DESCRIPTION

Various embodiments of the invention are directed to systems, methods,and articles of manufacture for recognizing gestures in a singleembodiment or in multiple embodiments. Other objects, features, andadvantages of the invention are described in the detailed description,figures, and claims.

Various embodiments will now be described in detail with reference tothe drawings, which are provided as illustrative examples of theinvention so as to enable those skilled in the art to practice theinvention. Notably, the figures and the examples below are not meant tolimit the scope of the present invention. Where certain elements of thepresent invention may be partially or fully implemented using knowncomponents (or methods or processes), only those portions of such knowncomponents (or methods or processes) that are necessary for anunderstanding of the present invention will be described, and thedetailed descriptions of other portions of such known components (ormethods or processes) will be omitted so as not to obscure theinvention. Further, various embodiments encompass present and futureknown equivalents to the components referred to herein by way ofillustration.

The gesture recognition systems may be implemented independently ofmixed reality systems, but some embodiments below are described inrelation to MR/AR systems for illustrative purposes only. Further, thegesture recognition systems described herein may also be used in anidentical manner with VR systems.

Illustrative Mixed Reality Scenario and System

The description that follows pertains to an illustrative augmentedreality system with which the gesture recognition system may bepracticed. However, it is to be understood that the embodiments alsolends themselves to applications in other types of display systems(including other types of mixed reality systems), and therefore theembodiments are not to be limited to only the illustrative systemdisclosed herein.

Mixed reality (e.g., AR) scenarios often include presentation of virtualcontent (e.g., images and sound) corresponding to virtual objects inrelationship to real-world objects. For example, referring to FIG. 1 ,an augmented reality scene 100 is depicted wherein a user of an ARtechnology sees a real-world, physical, park-like setting 102 featuringpeople, trees, buildings in the background, and a real-world, physicalconcrete platform 104. In addition to these items, the user of the ARtechnology also perceives that he “sees” a virtual robot statue 106standing upon the real-world, physical platform 104, and a virtualcartoon-like avatar character 108 flying by which seems to be apersonification of a bumblebee, even though these virtual objects 106,108 do not exist in the real world.

Like AR scenarios, VR scenarios can also receive user input fromgestures to allow interaction with virtual/digital objects in thescenarios. Accurately recognizing user gestures can improve the AR/VRscenarios.

The description that follows pertains to an illustrative augmentedreality system with which the invention may be practiced. However, it isto be understood that the invention also lends itself to applications inother types of augmented reality and virtual reality systems, andtherefore the invention is not to be limited to only the illustrativesystem disclosed herein.

Referring to FIG. 2 , one embodiment of an augmented reality system 200constructed in accordance with present embodiments will now bedescribed. The augmented reality system 200 may include one or more atleast partially transparent surfaces through which the ambientenvironment can be seen and through which the augmented reality system200 produces images of virtual objects (e.g., using one or more lightprojectors).

The augmented reality system 200 includes a frame structure 202 worn bya user 250, a display system 204 carried by the frame structure 202,such that the display system 204 is positioned in front of the eyes ofthe user 250, and a speaker 206 and a FOV camera 208 incorporated intoor connected to the frame structure 202. In the illustrated embodiment,the speaker 206 is carried by the frame structure 202, such that thespeaker 206 is positioned adjacent (in or around) the ear canal of theuser 250, e.g., an earbud or headphone. In the illustrated embodiment,the FOV camera 208 is carried by the frame structure 202, such that theFOV camera 208 is forward facing and adjacent the user's eyes. Theaugmented reality system 200 may be operated in conjunction with agesture recognition subsystem 220, and operatively coupled by a wired orwireless connection 210 thereto.

The gesture recognition subsystem 220 includes an object recognizer 222,a geometric analyzer 224, and a memory (“RAM”) 226. The objectrecognizer 222 is configured to process image data and identify objectstherein. The geometric analyzer 224 is configured to process object dataand identify geometric characteristics thereof. The identified objectsand corresponding geometric characteristics can be stored in the RAM226.

The forward facing FOV camera 208 may be employed for any number ofpurposes, such as recording of images/video from the forward directionof the system 200. In addition, the FOV cameras 208 may be used tocapture information about the environment in which the user 250 islocated, such as information indicative of distance, orientation, and/orangular position of the user 250 with respect to that environment andspecific objects in that environment. The FOV cameras 208 may also beused to capture information about the user's hands. That information maybe analyzed by the gesture recognition subsystem 220 to attempt torecognize a gesture for user input.

The augmented reality system 200 may further include one or more sensorsmounted to the frame structure 202 for detecting the position (includingorientation) and movement of the head of the user 250 and/or the eyeposition and inter-ocular distance of the user 250. Such sensor(s) mayinclude image capture devices, microphones, inertial measurement units(IMUs), accelerometers, compasses, GPS units, radio devices, and/orgyros. For example, in one embodiment, the augmented reality system 200comprises a head worn transducer subsystem that includes one or moreinertial transducers to capture inertial measures indicative of movementof the head of the user 250. Such devices may be used to sense, measure,or collect information about the head movements of the user 250. Forinstance, these devices may be used to detect/measure movements, speeds,acceleration and/or positions of the head of the user 250. The position(including orientation) of the head of the user 250 is also known as theuser 250 “head pose.”

The augmented reality system 200 may further include rearward facingcameras to track angular position (the direction in which the eye oreyes are pointing), blinking, and depth of focus (by detecting eyeconvergence) of the eyes of the user 250. Such eye tracking informationmay, for example, be discerned by projecting light at the end user'seyes, and detecting the return or reflection of at least some of thatprojected light.

The augmented reality system 200 further comprises a control subsystem(not shown) that may take any of a large variety of forms. The controlsubsystem includes a number of controllers, for instance one or moremicrocontrollers, microprocessors or central processing units (CPUs),digital signal processors, graphics processing units (GPUs), otherintegrated circuit controllers, such as application specific integratedcircuits (ASICs), programmable gate arrays (PGAs), for instance fieldPGAs (FPGAs), and/or programmable logic controllers (PLUs). The controlsubsystem may be separate from the gesture recognition subsystem 220 ormay include the gesture recognition subsystem 220.

The various processing components of the augmented reality system 200may be physically contained in a distributed subsystem. For example, theaugmented reality system 200 comprises a local processing and datamodule operatively coupled, such as by a wired lead or wirelessconnectivity 210, to a portion of the display subsystem 204. The localprocessing and data module may be mounted in a variety ofconfigurations, such as fixedly attached to the frame structure 202,fixedly attached to a helmet or hat, embedded in headphones, removablyattached to the torso of the user 250, or removably attached to the hipof the user 250 in a belt-coupling style configuration. The augmentedreality system 200 may further include a remote processing module andremote data repository operatively coupled, such as by a wired lead orwireless connectivity to the local processing and data module, such thatthese remote modules are operatively coupled to each other and availableas resources to the local processing and data module. The localprocessing and data module may comprise a power-efficient processor orcontroller, as well as digital memory, such as flash memory, both ofwhich may be utilized to assist in the processing, caching, and storageof data captured from the sensors and/or acquired and/or processed usingthe remote processing module and/or remote data repository, possibly forpassage to the display subsystem 204 after such processing or retrieval.The remote processing module may comprise one or more relativelypowerful processors or controllers configured to analyze and processdata and/or image information. The remote data repository may comprise arelatively large-scale digital data storage facility, which may beavailable through the internet or other networking configuration in a“cloud” resource configuration. In one embodiment, all data is storedand all computation is performed in the local processing and datamodule, allowing fully autonomous use from any remote modules. Thecouplings between the various components described above may include oneor more wired interfaces or ports for providing wires or opticalcommunications, or one or more wireless interfaces or ports, such as viaRF, microwave, and IR for providing wireless communications. In someimplementations, all communications may be wired, while in otherimplementations all communications may be wireless, with the exceptionof the optical fiber(s).

Summary of Problems and Solutions

The inaccuracy and lack of repeatability in current gesture recognitionsystems can result in user input errors that can frustrate users. Theembodiments described herein identify the centroid and various surfacenormals of a user's hand. By comparing these geometric characteristicsof a user's hand, the embodiments described herein more accuratelyrecognize user gestures, therein improving user input.

Gesture Recognition Systems and Methods

In some implementations, the AR system may detect and be responsive toone or more finger/hand gestures. These gestures can take a variety offorms and may, for example, be based on inter-finger interaction,pointing, tapping, rubbing, etc. Other gestures may, for example,include 2D or 3D representations of characters (e.g., letters, digits,punctuation). To enter such, a user swipes their finger in the definedcharacter pattern. Other gestures may include thumb/wheel selection typegestures, which may, for example be used with a “popup” circular radialmenu which may be rendered in a field of view of a user, according toone illustrated embodiment.

Embodiments of the AR system can therefore recognize various commandsusing gestures, and in response perform certain functions mapped to thecommands. The mapping of gestures to commands may be universallydefined, across many users, facilitating development of variousapplications which employ at least some commonality in user interface.Alternatively or additionally, users or developers may define a mappingbetween at least some of the gestures and corresponding commands to beexecuted by the AR system in response to detection of the commands.

For example, a pointed index finger may indicate a command to focus, forexample to focus on a particular portion of a scene or virtual contentat which the index finger is pointed. A pinch gesture can be made withthe tip of the index finger touching a tip of the thumb to form a closedcircle, e.g., to indicate a grab and/or copy command. Another examplepinch gesture can be made with the tip of the ring finger touching a tipof the thumb to form a closed circle, e.g., to indicate a selectcommand.

Yet another example pinch gesture can be made with the tip of the pinkiefinger touching a tip of the thumb to form a closed circle, e.g., toindicate a back and/or cancel command. A gesture in which the ring andmiddle fingers are curled with the tip of the ring finger touching a tipof the thumb may indicate, for example, a click and/or menu command.Touching the tip of the index finger to a location on the head worncomponent or frame may indicate a return to home command.

Embodiments of the invention provide an advanced system and method forperforming gesture tracking and identification. In one embodiment, arejection cascade approach is performed, where multiple stages ofgesture analysis is performed upon image data to identify gestures. Asshown in the cascade 3600 of FIG. 3 , incoming images (e.g., an RGBimage at a depth D) is processed using a series of permissive analysisnodes. Each analysis node performs a distinct step of determiningwhether the image is identifiable as a gesture. Each stage in thisprocess (i.e., analysis node) performs a targeted computation so thatthe sequence of stages/analysis nodes can be used to efficiently performthe gesture processing. This means, for example, that the amount ofprocessing power at each stage of the process, along with thesequence/order of the nodes, can be used to optimize the ability toremove non-gestures while doing so with minimal computational expenses.For example, computationally less-expensive algorithms may be applied inthe earlier stages to remove large numbers of “easier” candidates,thereby leaving smaller numbers of “harder” data to be analyzed in laterstages using more computationally expensive algorithms.

The general approach to perform this type of processing in oneembodiment is shown in the flowchart 3601 of FIG. 4 . The first step isto generate candidates for the gesture processing (step 3602). Theseinclude, for example, images captured from sensor measurements of thewearable device, e.g., from camera(s) mounted on the wearable device.Next, analysis is performed on the candidates to generate analysis data(step 3604). For example, one type of analysis may be to check onwhether the contour of the shapes (e.g., fingers) in the image is sharpenough. Sorting is then performed on the analyzed candidates (step3606). Finally, any candidate that corresponds to a scoring/analysisvalue that is lower than a minimum threshold is removed fromconsideration (step 3608).

FIG. 5 depicts a more detailed approach 3650 for gesture analysisaccording to one embodiment of the invention. The first action is toperform depth segmentation upon the input data. For example, typicallythe camera providing the data inputs (e.g., the camera producingRGB+depth data) will be mounted on the user's head, where the camera FOV(field of view) will cover the range in which the human could reasonablyperform gestures. As shown in illustration 3660 of FIG. 6 , a linesearch can be performed through the data (e.g., from the bottom of theFOV).

If there are identifiable points along that line, then potentially agesture has been identified. Performing this analysis over a series oflines can be used to generate the depth data. In some embodiment, thistype of processing can be quite sparse—perhaps where 50 points areacquired relatively really quickly. Of course, different kinds of lineseries can be employed, e.g., in addition to or instead of flat linesacross the bottom, smaller diagonal lines are employed in the area wherethere might be a hand/arm.

Any suitable pattern may be employed, selecting ones that are mosteffective at detecting gestures. In some embodiments, aconfidence-enhanced depth map is obtained, where the data is floodfilled from cascade processing where a “flood fill” is performed tocheck for and filter whether the identified object is really a hand/arm.The confidence enhancement can be performed, for example, by getting aclear map of the hand and then checking for the amount of light that isreflected off the hand in the images to the sensor, where the greateramount of light corresponds to a higher confidence level to enhance themap.

From the depth data, one can cascade to perform immediate/fastprocessing, e.g., where the image data is amenable to very fastrecognition of a gesture. This works best for very simple gesturesand/or hand/finger positions.

In many cases, deeper processing is to be performed to augment the depthmap. For example, one type of depth augmentation is to perform depthtransforms upon the data. Another type of augmentation is to check forgeodesic distances from specified point sets, such as boundaries,centroids, etc. For example, from a surface location, a determination ismade of the distance to various points on the map. This attempts tofind, for example, the farthest point to the tip of the fingers (byfinding the end of the fingers). The point sets may be from theboundaries (e.g., outline of hand) or centroid (e.g., statisticalcentral mass location).

Surface normalization may also be calculated. In addition, curvaturesmay also be estimated, which identifies how fast a contour turns—and toperform a filtering process to go over the points and removing concavepoints from fingers. In some embodiments, orientation normalization maybe performed on the data. To explain, consider that a given image of thehand may be captured with the hand in different positions. However, theanalysis may be expecting a canonical position of the image data of thehand. In this situation, as shown in illustration 3670 of FIG. 7 , themapped data may be re-oriented to change to a normalized/canonical handposition.

One advantageous approach in some embodiments of invention is to performbackground subtraction on the data. In many cases, a known backgroundexists in a scene, e.g., the pattern of a background wall. In thissituation, the map of the object to be analyzed can be enhanced byremoving the background image data. An example of this process is shownin illustration 3680 of FIG. 8 , where the left portion of the figureshows an image of a hand over some background image data. The right-handportion of the figure shows the results of removing the background fromthe image, leaving the augmented hand data with increased clarity andfocus.

Depth comparisons may also be performed upon points in the image toidentify the specific points that pertain to the hand (as opposed to thebackground non-hand data). For example, as shown in illustration 3690 ofFIG. 9 , it can be seen a first point A is located at a first depth anda second point B is located at a significantly different second depth.In this situation, the difference in the depths of these two pointsmakes it very evident that they likely belong to different objects.Therefore, if one knows that the depth of the hand is at the same depthvalue as point A, then one can conclude that point A is part of thehand. On the other hand, since the depth value for point B is not thesame as the depth of the hand, then one can readily conclude that pointB is not part of the hand.

At this point a series of analysis stages is performed upon the depthmap. Any number of analysis stages can be applied to the data. Thepresent embodiment shows three stages, but one of ordinary skill in theart would readily understand that any other number of stages (eithersmaller or larger) may be used as appropriate for the application towhich the invention is applied.

In the current embodiment, stage 1 analysis is performed using aclassifier mechanism upon the data. For example, aclassification/decision forest can be used to apply a series of yes/nodecisions in the analysis to identify the different parts of the handfor the different points in the mapping.

This identifies, for example, whether a particular point belongs to thepalm portion, back of hand, non-thumb finger, thumb, fingertip, and/orfinger joint. Any suitable classifier can be used for this analysisstage. For example, a deep learning module or a neural network mechanismcan be used instead of or in addition to the classification forest. Inaddition, a regression forest (e.g., using a Hough transformation) canbe used in addition to the classification forest.

The next stage of analysis (stage 2) can be used to further analysis themapping data. For example, analysis can be performed to identify jointlocations, articular, or to perform skeletonization on the data.Illustration 3695 of FIG. 10 provides an illustration ofskeletonization, where an original map of the hand data is used toidentify the locations of bones/joints within the hand, resulting in atype of “stick” figure model of the hand/hand skeleton. This type ofmodel provides with clarity a very distinct view of the location of thefingers and the specific orientation and/or configuration of the handcomponents. Labelling may also be applied at this stage to the differentparts of the hand.

At this point, it is possible that the data is now directly consumableby a downstream application without requiring any further analysis. Thismay occur, for example, if the downstream application itself includeslogic to perform additional analysis/computations upon the model data.In addition, the system can also optionally cascade to performimmediate/fast processing, e.g., where the data is amenable to very fastrecognition of a gesture, such as the (1) first gesture; (2) open palmgesture; (3) finger gun gesture; (4) pinch; (5) etc. This processing mayinclude using a neural network with buckets with confidence values. Forexample, as shown in illustration 3698 of FIG. 11 , various points onthe hand mapping (e.g., point on extended thumb and point on extendedfirst finger) can be used to immediately identify a pointing gesture.The outputs will then proceed to a world engine, e.g., to take actionupon a recognized gesture.

In addition, deeper processing can be performed in the stage 3 analysis.This may involve, for example, using a decision forest/tree to classifythe gesture. This additional processing can be used to identify thegesture, determine a hand pose, identify context dependencies, and/orany other information as needed.

Prior/control information can be applied in any of the described stepsto optimize processing. This permits some biasing for the analysisactions taken in that stage of processing. For example, for gameprocessing, previous action taken in the game can be used to bias theanalysis based upon earlier hand positions/poses. In addition, aconfusion matrix can be used to more accurately perform the analysis.

Using the principles of gesture recognition discussed above, the ARsystem may use visual input gathered from the user's FOV cameras andrecognize various gestures that may be associated with a predeterminedcommand or action. Referring now to flowchart 3700 of FIG. 12 , in step3102, the AR system may detect a gesture as discussed in detail above.In some embodiments, the AR system may detect one or more gestures, forexample, a series of gestures.

As described above, the movement of the fingers (e.g., one or moregestures) may be compared to a database to detect a predeterminedcommand, in step 3104. The AR system recognizes a command in step 3106.If the one or more gestures do correspond to any known command, the ARsystem determines the desired action and/or desired virtual contentbased on the one or more gestures, in step 3108. If the one or moregestures do not correspond to any known command, the AR system simplygoes back to detecting other gestures or movements to step 3102.

In step 3108, the AR system determines the type of action necessary inorder to satisfy the command. For example, the user may want to switchan application, or may want to turn a page, may want to generate a userinterface, may want to connect to a friend located at another physicallocation, etc. Based on the desired action/virtual content, the ARsystem determines whether to retrieve information from the cloudservers, or whether the action can be performed using local resources onthe user device, in step 3110.

For example, if the user simply wants to turn a page of a virtual book,the required data may already have been downloaded or may resideentirely on the local device, in which case, the AR system simplyretrieves data associated with the next page and may display the nextpage to the user. Similarly, if the user wants to create a userinterface such that the user can draw a picture in the middle of space,the AR system may simply generate a virtual drawing surface in thedesired location without needing data from the cloud.

Data associated with many applications and capabilities may be stored onthe local device such that the user device does not need tounnecessarily connect to the cloud or access the passable world model.Thus, if the desired action can be performed locally, local data may beused to display virtual content corresponding to the detected gesture(step 3112).

Alternatively, in step 3114, if the system needs to retrieve data fromthe cloud or the passable world model, the system may send a request tothe cloud network, retrieve the appropriate data and send it back to thelocal device such that the action or virtual content may beappropriately displayed to the user. For example, if the user wants toconnect to a friend at another physical location, the AR system may needto access the passable world model to retrieve the necessary dataassociated with the physical form of the friend in order to render itaccordingly at the local user device.

Thus, based on the user's interaction with the AR system, the AR systemmay create many types of user interfaces as desired by the user. Thefollowing represent some exemplary embodiments of user interfaces thatmay be created in a similar fashion to the exemplary process describedabove.

It should be appreciated that the above process is simplified forillustrative purposes, and other embodiments may include additionalsteps based on the desired user interface. The following discussion goesthrough various types of finger gestures, that may all be recognized andused such that the AR system automatically performs an action and/orpresents virtual content to the user that is either derived from thecloud or retrieved locally.

Finger Gestures

Finger gestures can take a variety of forms and may, for example, bebased on inter-finger interaction, pointing, tapping, rubbing, etc.

Other gestures may, for example, include 2D or 3D representations ofcharacters (e.g., letters, digits, punctuation). To enter such, a userswipes their finger in the defined character pattern. In oneimplementation of a user interface, the AR system renders three circles,each circle with specifically chosen characters (e.g., letters, digits,punctuation) arranged circumferentially around the periphery. The usercan swipe through the circles and letters to designate a characterselection or input. In another implementation, the AR system renders akeyboard (e.g., QWERTY keyboard) low in the user's field of view,proximate a position of the user's dominate hand in a bent-arm position.The user can than perform a swipe-like motion through desired keys, andthen indicate that the swipe gesture selection is complete by performinganother gesture (e.g., thumb-to-ring finger gesture) or otherproprioceptive interaction.

Other gestures may include thumb/wheel selection type gestures, whichmay, for example be used with a “popup” circular radial menu which maybe rendered in a field of view of a user, according to one illustratedembodiment.

Gestures 3800 of FIG. 13 shows a number of additional gestures. The ARsystem recognizes various commands, and in response performs certainfunctions mapped to the commands. The mapping of gestures to commandsmay be universally defined, across many users, facilitating developmentof various applications which employ at least some commonality in userinterface. Alternatively or additionally, users or developers may definea mapping between at least some of the gestures and correspondingcommands to be executed by the AR system in response to detection of thecommands.

In the top row left-most position, a pointed index finger may indicate acommand to focus, for example to focus on a particular portion of ascene or virtual content at which the index finger is pointed. In thetop row middle position, a first pinch gesture with the tip of the indexfinger touching a tip of the thumb to form a closed circle may indicatea grab and/or copy command. In the top row right-most position, a secondpinch gesture with the tip of the ring finger touching a tip of thethumb to form a closed circle may indicate a select command.

In the bottom row left-most position, a third pinch gesture with the tipof the pinkie finger touching a tip of the thumb to form a closed circlemay indicate a back and/or cancel command. In the bottom row middleposition, a gesture in which the ring and middle fingers are curled withthe tip of the ring finger touching a tip of the thumb may indicate aclick (e.g., right click) and/or menu command. In the bottom rowright-most position, touching the tip of the index finger to a locationon the head worn component or frame may indicate a return to homecommand. Such may cause the AR system to return to a home or defaultconfiguration, for example displaying a home or default menu.

It should be appreciated that there may be many more types of user inputnot limited to the ones discussed above. For example, the system maymeasure neurological signals and use that as an input for the system.The system may have a sensor that tracks brain signals and map itagainst a table of commands. In other words, the user input is simplythe user's thoughts, that may be measured by the user's brain signals.This may also be referred to as subvocalization sensing. Such a systemmay also include apparatus for sensing EEG data to translate the user's“thoughts” into brain signals that may be decipherable by the system.

Hand Centroid Gesture Recognition Systems and Methods “L”-Shaped Gesture

FIGS. 14-20 depict a hand centroid gesture recognition system accordingto one embodiment. FIG. 14 depicts an image 300 of a user's right hand302. This image may have been acquired using a front facing FOV camera208. The user's hand 302 is making an “L”-shaped gesture by positioninga thumb 304 and a first finger 306 at an almost right angle to eachother.

In one embodiment, the object recognizer 222 in the gesture recognitionsubsystem 220 identifies the hand 302 in the image. The objectrecognizer 222 receives the image data from the front facing FOV camera208 and/or the RAM 226. The object recognizer 222 may identify the hand302 as a hand using the methods described above. Data relating to theidentification of the hand 302 is stored in the RAM 226.

FIG. 15 depicts map points 308, 310, 312 identified in the image 300 ofthe hand 302. These map points correspond to a hand centroid 308, athumb tip 310, and a first fingertip 312. In some embodiments, fewer ormore map points may be identified. For example, one, two, eight,seventeen, or more points may be identified. In some embodiments, one ormore images of the hand may be used to determine a 3D representation ofthe hand 302.

In one embodiment, the object recognizer 222 and/or the geometricanalyzer 224 in the gesture recognition subsystem 220 identifies the mappoints correspond to the hand centroid 308, the thumb tip 310, and thefirst fingertip 312 in the image. The object recognizer 222 and/or thegeometric analyzer 224 receives the image data from the front facing FOVcamera 208 and/or the RAM 226. The object recognizer 222 and/or thegeometric analyzer 224 may identify the map points 308, 310, 312 usingthe methods described above and/or geometric analysis methods. Datarelating to the map points 308, 310, 312 in the image 300 of the hand302 is stored in the RAM 226.

FIG. 16 depicts surface normals 314, 316, 318 at the map points 308,310, 312 identified in the image 300 of the hand 302. The surface normal314 at the hand centroid map point 308 is on a caudal surface of thehand 302. The surface normals 316, 318 at the thumb tip and firstfingertip map points 310, 312 are on a surface defined by the extendedthumb 304 and finger 306.

In one embodiment, the geometric analyzer 224 in the gesture recognitionsubsystem 220 identifies the surface normals 314, 316, 318 at the mappoints 308, 310, 312 in the image. The geometric analyzer 224 receivesthe image and map point data from the front facing FOV camera 208 and/orthe RAM 226. The geometric analyzer 224 may identify the surface normals314, 316, 318 using geometric analysis methods. Data relating to thesurface normals 314, 316, 318 in the image 300 of the hand 302 is storedin the RAM 226.

Because these three surface normals 314, 316, 318 are substantiallyparallel (e.g., within 10 degrees of each other), the gesturerecognition subsystem 220 recognizes the gesture as an “L”-shape. Insome embodiments, the gesture recognition subsystem 220, for “L”-shapegestures, determines an angle θ between map points 312, 308, and 310. Insome embodiments, determining that θ is approximately 90 degrees is partof the gesture recognition subsystem 220 recognizing the gesture as an“L”-shape. In response to recognizing the “L”-shape gesture, theaugmented reality system 200 displays a cursor 320 at a locationadjacent the first fingertip map point 312, as shown in FIG. 17 . Theaugmented reality system 200 may “stick” the cursor 320 to the firstfingertip map point 312 to maintain the spatial relationship therebetween even when the first finger 306 moves. In some embodiments, theAR system 200 may project the cursor 320 into the environment based on arelationship of the map points 320, 308, and/or 310, for example, usingray casting.

In one embodiment, the geometric analyzer 224 in the gesture recognitionsubsystem 220 analyzes the surface normals 314, 316, 318 at the mappoints 308, 310, 312 in the image to determine whether they aresubstantially parallel. The geometric analyzer 224 receives the imageand map point data from the front facing FOV camera 208 and/or the RAM226. The geometric analyzer 224 may determine whether the surfacenormals 314, 316, 318 are substantially parallel using geometricanalysis methods. Data relating geometric relationship between thesurface normals 314, 316, 318 in the image 300 of the hand 302 and theidentified “L”-gesture is stored in the RAM 226.

FIGS. 18-20 depict a click command executed by a hand 302 displaying the“L”-gesture. FIG. 18 shows that the tip of the user's thumb 304 hasmoved behind the user's hand 302. FIG. 19 depicts in shadow a positionof the tip of the user's thumb 304, including the map point 310 at thethumb tip, as projected by the gesture recognition subsystem 220. FIG.20 depicts a line 322 calculated by the gesture recognition subsystem220 between the map points 312 and 308, from the first fingertip to thehand centroid. As the thumb tip 304 approaches line 322 to becomeoccluded by the hand at map point 310, 8 decreases in value. At athreshold limit of a change in the value of 8 (from 8 in FIGS. 16 to 8 ′in FIG. 20 ), in some embodiments less than about 30 degrees, thegesture recognition subsystem 220 identifies a click command executed bythe hand 302 displaying the “L”-gesture. In identifying a thresholdchange in the value of 8, the gesture recognition subsystem 220determines that the thumb tip 304 approaches line 322. In response toidentification of the click command, the augmented reality system 200executes a command (e.g., select, activate, close, etc.) at the locationof the cursor 320.

In one embodiment, the object recognizer 222 and/or the geometricanalyzer 224 in the gesture recognition subsystem 220 identifies themovement of the user's thumb 304 towards the position of map point 310in FIGS. 19 and 20 , projects the tip of the thumb 304, and analyzes thevarious map point 308, 310, 312 positions, all of which correspond toidentification of the click command. The object recognizer 222 and/orthe geometric analyzer 224 receives the image data from the front facingFOV camera 208 and/or the RAM 226. The object recognizer 222 and/or thegeometric analyzer 224 may identify, project, and analyze using themethods described above and/or geometric analysis methods. Data relatingto identification of the click command is stored in the RAM 226.

“C”-Shaped Gesture

FIGS. 21-26 depict a hand centroid gesture recognition system accordingto another embodiment. FIG. 21 depicts an image 300 of a user's righthand 302. This image may have been acquired using a front facing FOVcamera 208. The user's hand 302 is making a “C”-shaped gesture byselective positioning of a thumb 304 and a first finger 306 of the hand302.

In one embodiment, the object recognizer 222 in the gesture recognitionsubsystem 220 identifies the hand 302 in the image. The objectrecognizer 222 receives the image data from the front facing FOV camera208 and/or the RAM 226. The object recognizer 222 may identify the hand302 as a hand using the methods described above. Data relating to theidentification of the hand 302 is stored in the RAM 226.

FIG. 22 depicts map points 308, 310, 312 identified in the image 300 ofthe hand 302. These map points correspond to a hand centroid 308, athumb tip 310, and a first fingertip 312.

In one embodiment, the object recognizer 222 and/or the geometricanalyzer 224 in the gesture recognition subsystem 220 identifies the mappoints correspond to the hand centroid 308, the thumb tip 310, and thefirst fingertip 312 in the image. The object recognizer 222 and/or thegeometric analyzer 224 receives the image data from the front facing FOVcamera 208 and/or the RAM 226. The object recognizer 222 and/or thegeometric analyzer 224 may identify the map points 308, 310, 312 usingthe methods described above and/or geometric analysis methods. Datarelating to the map points 308, 310, 312 in the image 300 of the hand302 is stored in the RAM 226. In some embodiments, fewer or more mappoints may be identified. For example, one, two, eight, seventeen, ormore points may be identified. In some embodiments, one or more imagesof the hand may be used to determine a 3D representation of the hand302.

FIG. 23 depicts surface normals 314, 316, 318 at the map points 308,310, 312 identified in the image 300 of the hand 302. The surface normal314 at the hand centroid map point 308 is on a caudal surface of thehand 302. The surface normals 316, 318 at the thumb tip and firstfingertip map points 310, 312 are on a surface defined by the thumb 304and finger 306.

In one embodiment, the geometric analyzer 224 in the gesture recognitionsubsystem 220 identifies the surface normals 314, 316, 318 at the mappoints 308, 310, 312 in the image. The geometric analyzer 224 receivesthe image and map point data from the front facing FOV camera 208 and/orthe RAM 226. The geometric analyzer 224 may identify the surface normals314, 316, 318 using geometric analysis methods. Data relating to thesurface normals 314, 316, 318 in the image 300 of the hand 302 is storedin the RAM 226.

Because the surface normal at the hand centroid map point 308 issubstantially orthogonal (e.g., within 10 degrees of perpendicular) tothe respective surface normals 316, 318 at the thumb tip and firstfingertip map points 310, 312, the gesture recognition subsystem 220recognizes the gesture as an “C”-shape. In response to recognizing the“C”-shape gesture, the augmented reality system 200 displays a cursor320 at a location (e.g., midway) adjacent a line 324 between the thumbtip and the first fingertip map points 310, 312, as shown in FIG. 24 .The augmented reality system 200 may “stick” the cursor 320 to thelocation (e.g., midway) between the thumb tip and the first fingertipmap points 310, 312 to maintain the spatial relationship there betweeneven when the hand 302 moves.

In one embodiment, the geometric analyzer 224 in the gesture recognitionsubsystem 220 analyzes the surface normals 314, 316, 318 at the mappoints 308, 310, 312 in the image to determine whether they have thesubstantially orthogonal relationship described above. The geometricanalyzer 224 receives the image and map point data from the front facingFOV camera 208 and/or the RAM 226. The geometric analyzer 224 maydetermine whether the surface normals 314, 316, 318 have thesubstantially orthogonal relationship using geometric analysis methods.Data relating geometric relationship between the surface normals 314,316, 318 in the image 300 of the hand 302 and the identified “C”-gestureis stored in the RAM 226.

FIGS. 25-26 depict a click command executed by a hand 302 displaying the“C”-gesture. FIG. 25 shows that the tip of the user's thumb 304 and thetip of the user's first finger 306 have moved so that their positionsare substantially similar. In one embodiment, the gesture recognitionsubsystem 220 may recognize that the positions are substantially similarwhen the first fingertip map point 312 is within a certain radius 326 ofthe thumb tip map point 310, as shown in FIG. 26 . Because therespective positions of the tip of the user's thumb 304 and the tip ofthe user's first finger 306 are substantially similar, the gesturerecognition subsystem 220 identifies a click command executed by thehand 302 displaying the “C”-gesture. In response to identification ofthe click command, the augmented reality system 200 executes a command(e.g., select, activate, close, etc.) at the location of the cursor 320.

In one embodiment, the object recognizer 222 and/or the geometricanalyzer 224 in the gesture recognition subsystem 220 identifies themovement of the user's thumb 304 and/or first finger 306 and analyzesthe map point 312, 314 positions corresponding to their respective tips,all of which correspond to identification of the click command. Theobject recognizer 222 and/or the geometric analyzer 224 receives theimage data from the front facing FOV camera 208 and/or the RAM 226. Theobject recognizer 222 and/or the geometric analyzer 224 may identify andanalyze using the methods described above and/or geometric analysismethods. Data relating to identification of the click command is storedin the RAM 226.

While the gesture recognition embodiments described herein includeanalyzing images from front facing FOV cameras 208, the FOV of thecameras 208 may be larger than the FOV of the user (i.e., of the user'seyes). Accordingly, the “L”-shaped and/or “C”-shaped gestures describedabove may be used tactilely outside of the user's FOV, but within theFOV of the front facing FOV cameras 208. In one such embodiment, the“L”-shaped and/or “C”-shaped gestures may be used on a surface (e.g.,desktop, lap, etc.) to perform the functions of a virtual mouse.

System Architecture Overview

FIG. 27 is a block diagram of an illustrative computing system 1200suitable for implementing an embodiment of the present invention.Computer system 1200 includes a bus 1206 or other communicationmechanism for communicating information, which interconnects subsystemsand devices, such as processor 1207, system memory 1208 (e.g., RAM),static storage device 1209 (e.g., ROM), disk drive 1210 (e.g., magneticor optical), communication interface 1214 (e.g., modem or Ethernetcard), display 1211 (e.g., CRT or LCD), input device 1212 (e.g.,keyboard), and cursor control.

According to one embodiment of the invention, computer system 1200performs specific operations by processor 1207 executing one or moresequences of one or more instructions contained in system memory 1208.Such instructions may be read into system memory 1208 from anothercomputer readable/usable medium, such as static storage device 1209 ordisk drive 1210. In alternative embodiments, hard-wired circuitry may beused in place of or in combination with software instructions toimplement the invention. Thus, embodiments of the invention are notlimited to any specific combination of hardware circuitry and/orsoftware. In one embodiment, the term “logic” shall mean any combinationof software or hardware that is used to implement all or part of theinvention.

The term “computer readable medium” or “computer usable medium” as usedherein refers to any medium that participates in providing instructionsto processor 1207 for execution. Such a medium may take many forms,including but not limited to, non-volatile media and volatile media.Non-volatile media includes, for example, optical or magnetic disks,such as disk drive 1210. Volatile media includes dynamic memory, such assystem memory 1208.

Common forms of computer readable media includes, for example, floppydisk, flexible disk, hard disk, magnetic tape, any other magneticmedium, CD-ROM, any other optical medium, punch cards, paper tape, anyother physical medium with patterns of holes, RAM, PROM, EPROM,FLASH-EPROM (e.g., NAND flash, NOR flash), any other memory chip orcartridge, or any other medium from which a computer can read.

In an embodiment of the invention, execution of the sequences ofinstructions to practice the invention is performed by a single computersystem 1200. According to other embodiments of the invention, two ormore computer systems 1200 coupled by communication link 1215 (e.g.,LAN, PTSN, or wireless network) may perform the sequence of instructionsrequired to practice the invention in coordination with one another.

Computer system 1200 may transmit and receive messages, data, andinstructions, including program, i.e., application code, throughcommunication link 1215 and communication interface 1214. Receivedprogram code may be executed by processor 1207 as it is received, and/orstored in disk drive 1210, or other non-volatile storage for laterexecution. Database 1232 in storage medium 1231 may be used to storedata accessible by system 1200 via data interface 1233.

The invention includes methods that may be performed using the subjectdevices. The methods may comprise the act of providing such a suitabledevice. Such provision may be performed by the user. In other words, the“providing” act merely requires the user obtain, access, approach,position, set-up, activate, power-up or otherwise act to provide therequisite device in the subject method. Methods recited herein may becarried out in any order of the recited events which is logicallypossible, as well as in the recited order of events.

Exemplary aspects of the invention, together with details regardingmaterial selection and manufacture have been set forth above. As forother details of the present invention, these may be appreciated inconnection with the above-referenced patents and publications as well asgenerally known or appreciated by those with skill in the art. The samemay hold true with respect to method-based aspects of the invention interms of additional acts as commonly or logically employed.

In addition, though the invention has been described in reference toseveral examples optionally incorporating various features, theinvention is not to be limited to that which is described or indicatedas contemplated with respect to each variation of the invention. Variouschanges may be made to the invention described and equivalents (whetherrecited herein or not included for the sake of some brevity) may besubstituted without departing from the true spirit and scope of theinvention. In addition, where a range of values is provided, it isunderstood that every intervening value, between the upper and lowerlimit of that range and any other stated or intervening value in thatstated range, is encompassed within the invention.

Also, it is contemplated that any optional feature of the inventivevariations described may be set forth and claimed independently, or incombination with any one or more of the features described herein.Reference to a singular item, includes the possibility that there areplural of the same items present. More specifically, as used herein andin claims associated hereto, the singular forms “a,” “an,” “said,” and“the” include plural referents unless the specifically stated otherwise.In other words, use of the articles allow for “at least one” of thesubject item in the description above as well as claims associated withthis disclosure. It is further noted that such claims may be drafted toexclude any optional element. As such, this statement is intended toserve as antecedent basis for use of such exclusive terminology as“solely,” “only” and the like in connection with the recitation of claimelements, or use of a “negative” limitation.

Without the use of such exclusive terminology, the term “comprising” inclaims associated with this disclosure shall allow for the inclusion ofany additional element-irrespective of whether a given number ofelements are enumerated in such claims, or the addition of a featurecould be regarded as transforming the nature of an element set forth insuch claims. Except as specifically defined herein, all technical andscientific terms used herein are to be given as broad a commonlyunderstood meaning as possible while maintaining claim validity.

The breadth of the present invention is not to be limited to theexamples provided and/or the subject specification, but rather only bythe scope of claim language associated with this disclosure.

In the foregoing specification, the invention has been described withreference to specific embodiments thereof. It will, however, be evidentthat various modifications and changes may be made thereto withoutdeparting from the broader spirit and scope of the invention. Forexample, the above-described process flows are described with referenceto a particular ordering of process actions. However, the ordering ofmany of the described process actions may be changed without affectingthe scope or operation of the invention. The specification and drawingsare, accordingly, to be regarded in an illustrative rather thanrestrictive sense.

1. A method of executing a gesture command, comprising: identifying apoint of a hand between a wrist and a base of fingers of the hand;identifying a first finger tip of a first finger on the hand;identifying a thumb tip of a thumb on the hand; determining surfacenormals respectively at the point of the hand, the first fingertip, andthe thumb tip; computing angles between the respective surface normals;determining that the respective surface normals at the point of the handon a caudal surface of the hand, at the first fingertip, and at thethumb tip are substantially parallel based on the computed anglesbetween the respective surface normal; and determining an L-shapedgesture of the hand based at least in part on determining that therespective surface normals at the point of the hand on a caudal surfaceof the hand, at the first fingertip, and at the thumb tip aresubstantially parallel.
 2. The method of claim 1, further comprising:determining an angle between the first fingertip, the point of the hand,and the thumb tip, and determining the L-shaped gesture of the handbased at least in part on determining the angle is approximately 90degrees.
 3. The method of claim 1, further comprising displaying acursor in a field of view at a location corresponding to the firstfingertip in response to determining the L-shaped gesture.
 4. The methodof claim 3, further comprising: detecting a movement of the thumb tip toa mapped planar position between the point of the hand and the firstfingertip; and executing a command at the cursor location in response todetecting the movement.
 5. The method of claim 3, further comprisingmaintaining the cursor at the location corresponding to the firstfingertip after the first finger moves.
 6. The method of claim 1,further comprising: calculating a first line between the first fingertipand the point of the hand; calculating a second line between the thumbtip and the point of the hand; determining an angular relationshipbetween the first and second lines; and determining a gesture of thehand based on the determined angular relationship between the first andsecond lines.
 7. The method of claim 6, further comprising: determiningthat the first and second lines are substantially orthogonal based onthe determined angular relationship between the first and second lines;and determining the L-shaped gesture of the hand based at least in parton determining the first and second lines are substantially orthogonal.8. The method of claim 6, wherein a virtual cursor is displayed in afield of view at a location corresponding to the first fingertip.
 9. Themethod of claim 8, further comprising: detecting a change in the angularrelationship between the first and second lines; and executing a commandat the cursor location in response to detecting the change in theangular relationship between the first and second lines.
 10. The methodof claim 9, wherein the change in the angular relationship between thefirst and second lines is a threshold amount of decrease in an anglebetween first and second lines.
 11. The method of claim 10, wherein thethreshold amount of decrease is about 30 degrees.
 12. The method ofclaim 1, wherein the point of the hand is a hand centroid.